273 lines
9.1 KiB
Rust
273 lines
9.1 KiB
Rust
use crate::ast::{Expr, Number};
|
|
use std::io::{Read, BufReader};
|
|
|
|
pub type ReadResult = Result<Expr, String>;
|
|
|
|
pub struct ExprReader {
|
|
read_stack: Vec<char>
|
|
}
|
|
|
|
impl ExprReader {
|
|
|
|
fn new() -> ExprReader {
|
|
ExprReader {
|
|
read_stack: vec![]
|
|
}
|
|
}
|
|
|
|
fn get_char<T: Read>(&mut self, reader: &mut BufReader<T>, skip_whitespace: bool) -> Option<char> {
|
|
loop {
|
|
match self.read_stack.pop() {
|
|
Some(c) if !c.is_whitespace() || !skip_whitespace =>
|
|
{
|
|
return Some(c)
|
|
},
|
|
Some(_) => continue,
|
|
None => ()
|
|
};
|
|
|
|
// Rust is weird, it doesn't provide a way to read from a buffer char by char.
|
|
let mut single_char_buff = [0];
|
|
let bytes_read = reader.read(&mut single_char_buff);
|
|
match bytes_read {
|
|
Ok(n) if n > 0 => {},
|
|
Ok(_) => return None,
|
|
Err(_) => return None
|
|
};
|
|
let ch = single_char_buff[0] as char;
|
|
|
|
match ch {
|
|
c if !c.is_whitespace() || !skip_whitespace => return Some(c),
|
|
_ => (),
|
|
};
|
|
}
|
|
}
|
|
|
|
fn unget_char(&mut self, c: char) {
|
|
self.read_stack.push(c);
|
|
}
|
|
|
|
// Look ahead. AFAIK Rust doesn't provide any unread functoinality like Java input streams which
|
|
// sucks.
|
|
fn peek_char<T: Read>(&mut self, reader: &mut BufReader<T>, skip_whitespace: bool) -> Option<char> {
|
|
match self.get_char(reader, skip_whitespace) {
|
|
Some(c) => {
|
|
self.unget_char(c);
|
|
Some(c)
|
|
},
|
|
None => None
|
|
}
|
|
}
|
|
|
|
fn read_quoted_expr<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
let rest = self.read_expr(reader)?;
|
|
Ok(Expr::Cons(Box::new(Expr::Symbol("quote".to_string())), Box::new(rest)))
|
|
}
|
|
|
|
fn read_unquoted_expr<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
match self.peek_char(reader, true) {
|
|
Some('@') => {
|
|
// Move forward in the buffer since we peeked it
|
|
let _ = self.get_char(reader, true);
|
|
let rest = self.read_expr(reader)?;
|
|
Ok(Expr::Cons(Box::new(Expr::Symbol("unquote-splicing".to_string())),
|
|
Box::new(rest)))
|
|
},
|
|
_ => {
|
|
let rest = self.read_expr(reader)?;
|
|
Ok(Expr::Cons(Box::new(Expr::Symbol("unquote".to_string())),
|
|
Box::new(rest)))
|
|
}
|
|
}
|
|
}
|
|
|
|
fn read_quasiquoted_expr<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
let rest = self.read_expr(reader)?;
|
|
Ok(Expr::Cons(Box::new(Expr::Symbol("quasiquote".to_string())),
|
|
Box::new(rest)))
|
|
}
|
|
|
|
// TODO: We might want to replace Cons with an actual List struct
|
|
fn read_list<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
let first = match self.read_expr(reader) {
|
|
Ok(value) => value,
|
|
Err(e) => match self.get_char(reader, true) {
|
|
// is it an empty list ?
|
|
// TODO: we might want to return an actual empty list here
|
|
Some(')') => return Ok(Expr::Nil),
|
|
_ => return Err(e)
|
|
}
|
|
};
|
|
let rest = match self.get_char(reader, true) {
|
|
Some(e) => {
|
|
self.unget_char(e);
|
|
self.read_list(reader)?
|
|
},
|
|
None => return Err("Unexpected EOF, expected . or symbol".to_string())
|
|
};
|
|
|
|
Ok(Expr::Cons(Box::new(first), Box::new(rest)))
|
|
}
|
|
|
|
fn is_valid_for_identifier(&self, c: char) -> bool {
|
|
match c {
|
|
'!' | '$' | '%' | '&' | '*' | '+' | '-' | '.' | '~' |
|
|
'/' | ':' | '<' | '=' | '>' | '?' | '@' | '^' | '_' |
|
|
'a'..='z' | 'A'..='Z' | '0'..='9' => true,
|
|
_ => false
|
|
}
|
|
}
|
|
|
|
fn _read_symbol<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
let mut symbol = match self.peek_char(reader, false) {
|
|
Some(e) if self.is_valid_for_identifier(e) => {
|
|
// Read into string
|
|
let ch = self.get_char(reader, false).unwrap();
|
|
let mut s = String::new();
|
|
s.push(ch);
|
|
s
|
|
},
|
|
Some(e) => {
|
|
return Err(format!("Unexpected character: got {}, expected a symbol", e))
|
|
},
|
|
None => return Err("Unexpected EOF".to_string())
|
|
};
|
|
|
|
loop {
|
|
match self.get_char(reader, false) {
|
|
Some(v) if self.is_valid_for_identifier(v) => symbol.push(v),
|
|
Some(v) => {
|
|
self.unget_char(v);
|
|
break;
|
|
},
|
|
None => break
|
|
}
|
|
}
|
|
|
|
Ok(Expr::Symbol(symbol))
|
|
}
|
|
|
|
fn read_escape_char<T: Read>(&mut self, reader: &mut BufReader<T>) -> Option<char> {
|
|
match self.get_char(reader, false) {
|
|
Some(e) => match e {
|
|
'\"' => Some('\"'),
|
|
'\'' => Some('\''),
|
|
'\\' => Some('\\'),
|
|
'n' => Some('\n'),
|
|
'r' => Some('\r'),
|
|
't' => Some('\t'),
|
|
_ => None
|
|
},
|
|
None => None
|
|
}
|
|
}
|
|
|
|
fn read_string<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
// Skip the " char
|
|
let _ = self.get_char(reader, false);
|
|
|
|
let mut string = "".to_string();
|
|
loop {
|
|
match self.get_char(reader, false) {
|
|
Some(e) => match e {
|
|
'\"' => break,
|
|
'\\' => match self.read_escape_char(reader) {
|
|
Some(v) => string.push(v),
|
|
None => return Err(format!("Unexpected char to escape, got {}", e))
|
|
},
|
|
//'\n' => return Err("Unescaped newlines are not allowed in string literals".to_string()),
|
|
_ => string.push(e)
|
|
},
|
|
None => return Err("Unexpected EOF while scanning a string".to_string())
|
|
}
|
|
}
|
|
Ok(Expr::Str(string))
|
|
}
|
|
|
|
fn read_number<T: Read>(&mut self, reader: &mut BufReader<T>, neg: bool) -> ReadResult {
|
|
let mut is_double = false;
|
|
let mut string = "".to_string();
|
|
loop {
|
|
match self.get_char(reader, false) {
|
|
Some(e) if e == '.' && is_double => return Err("A double with more that one '.' ???".to_string()),
|
|
Some(e) if e == '.' => {
|
|
is_double = true;
|
|
string.push(e);
|
|
}
|
|
Some(e) if e.is_digit(10) => string.push(e),
|
|
Some(e) => {
|
|
self.unget_char(e);
|
|
break;
|
|
}
|
|
None => break
|
|
}
|
|
}
|
|
if is_double {
|
|
Ok(Expr::Num(Number::Float(string.parse::<f64>().unwrap())))
|
|
} else {
|
|
Ok(Expr::Num(Number::Integer(string.parse::<i64>().unwrap())))
|
|
}
|
|
}
|
|
|
|
fn read_symbol<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
match self.peek_char(reader, true) {
|
|
Some(c) => match c {
|
|
'\"' => self.read_string(reader),
|
|
c if c.is_digit(10) => self.read_number(reader, false),
|
|
|
|
// ':' => self.read_keyword(reader),
|
|
// '-' => {
|
|
// Neg number
|
|
// }
|
|
_ => self._read_symbol(reader)
|
|
},
|
|
None => Err("Unexpected EOF while scanning atom".to_string())
|
|
}
|
|
}
|
|
|
|
pub fn read_expr<T: Read>(&mut self, reader: &mut BufReader<T>) -> ReadResult {
|
|
match self.get_char(reader, true) {
|
|
Some(c) => {
|
|
match c {
|
|
'\'' => self.read_quoted_expr(reader),
|
|
'~' => self.read_unquoted_expr(reader),
|
|
'`' => self.read_quasiquoted_expr(reader),
|
|
'(' => self.read_list(reader),
|
|
//'[' => self.read_vector(reader),
|
|
//'{' => self.read_map(reader),
|
|
_ => {
|
|
self.unget_char(c);
|
|
self.read_symbol(reader)
|
|
}
|
|
}
|
|
},
|
|
None => Ok(Expr::NoMatch)
|
|
}
|
|
}
|
|
|
|
pub fn read_from_buffer<T: Read>(&mut self, reader: &mut BufReader<T>) -> Result<Vec<Expr>, String> {
|
|
let mut ast = vec![];
|
|
loop {
|
|
match self.read_expr(reader) {
|
|
Ok(Expr::NoMatch) => break,
|
|
Err(v) => return Err(v),
|
|
Ok(v) => ast.push(v)
|
|
}
|
|
}
|
|
Ok(ast)
|
|
}
|
|
|
|
pub fn read(&mut self, string: &str) -> Result<Vec<Expr>, String> {
|
|
let reader = BufReader::new(string.as_bytes());
|
|
let mut buf_reader = BufReader::new(reader);
|
|
self.read_from_buffer(&mut buf_reader)
|
|
}
|
|
|
|
}
|
|
|
|
|
|
pub fn read_string(input: &str) -> Result<Vec<Expr>, String> {
|
|
let mut reader = ExprReader::new();
|
|
reader.read(input)
|
|
}
|